Packing gland for elastic-fluid turbines or the like



Sept. 13, 1927.

is. POCHOBRADSKY PACKING GLAND FOR ELASTIC FLUID TURBINES OR THE LIKEFil ed Oct 7, 1924 2 sham-sheet 1 Patented Sept. 13, 1927.

UNITED sTATEs PATENT OFFICE.

BEDRICI-I POOHOBB-ADSKY, OF SI DCUP, ENGLAND.

PACKING GLAND FOR ELASTIC-FLUID TURBINES OR THE LIKE.

Application filed Octobcr 7, 1924, Serial No. 742,096, and in GreatBritain October 20, 1923.

This invention relates to packing glands of the labyrinth type suitablefor machincry with rotating parts, such as elastic fluid turbines,turbo-compressors, water. turbines,

6 waterpumps or the like, and more particularly to packing glandsintended to be used to reduce leakage which is liable to take place atthe space where shafts pass through casings or diaphragms, or betweenthe ro- 10 tary and the stationary parts of the machine. v

according to the invention a packing gland of the labyrinth type has anumber of very small clearances, in which the leaking medium acquiresvelocity which is to a large extent destroyed in the larger spaces whichfollow each small clearance.

in packing glands of the labyrinth type so far known the smallclearances have been formed by plain surfaces or by a sharp edge and aplain surface, but it-has been found that owing to the plain surfacesany accidental contact has resulted in substantial damage to the glandsand consequent stoppage of the machines. According to the presentinvention, however, each of the small clearances is formed preferably bytwo sharp edges in close proximity, one sharp edge being formedon a ringor disc attached to a rotating part of the machine, the other sharpedgev being formed on a ring or disc attached to a stationary part ofthe machine. The saidrings or discs have a large surface so that anyheat generated by contact of sharp edges can be transmit ted readilythrough the large surfaces from the metal to the leaking medium.

Since the annular blades are provided with sharp edges it can be safelyarranged that the edges are in close proximity, since if they do touchthey are not damaged seriously but merely blunted. Moreover, in theevent of thesharp edges touching, the heat developed at the points ofcontact is not large, since the resisting force of the edges is notgreat, and it therefore follows that little heat has to be dissipated.Besides, since the clearance between the edges of the blades is so smallthe cooling effect of the steam on the edges is large as it flows fromone space past the intervening sharp blade edges with relatively highvelocity to enter the next space between sets of blades. As the steamenters the spacebetween sets of blades its progress ischecked anditsvelocin the direction of the flow from the preceding clearance, or bythe arrangement between the two successive clearances of abai'lle plateor baffle ring which causes a change in the direction of the flow of theleaking medium.

The sharp edges may be formed on rings turned out of a solid brush ordisc, or such rings may be made separately and built up into a packinggland by means of distance rings fastened securely to a box attachedeither to the stationary part or the rotating part of the machine. Therethe gland is subjected to high temperatures causing considerableexpansion, it is preferable-to make the stationary rings and therotating rings with the sharp'edges of the same material, or ofmaterials having approximately the same coefiicient of expansion, sothat the clearances will remain substantially constant whatever may bethe temperature produced by the steam flowing through the gland.Further, the rotating part of the gland is attached to the rotating partof the machine in such a way that the gland portion can expand freely inall directions, remaining concentric with the rotating part of themachine. This may be achieved by means of thin rings connecting thegland portion with the machine portion, the rings being flexible.Similarly, the stationary part of the gland is not attached rigidly tothe stationary portion of the machine, but by means of flexible rings orby means of four keys arranged crosswise, so that the stationary part ofthe gland can expand freely in all directions remaining concentric withthe rotating partof the gland.

- The invention will be described with reference to the accompanyingdrawings, of which Figure 1 is asectional view of a packin gland. Figure2 shows the section A-B through the shaft andthe portion of the glandattached to the shaft. Figures 3, 4,

5, 6 and 7 show various constructions of the labyrinths themselves.

Referring to Figure 1. a is a sleeve attached flexibly to the shaft; 7)is a stationary part of the gland attached flexibly to the casing. Thesleeve a is provided with rings having sharp edges. The sleeve l) is provided with rings 0 provided similarly with shar edges. Small clearancesare formed between the sharp edges of rings 0 and 0. These clearancesare not discernible in Fig. l, but may be seen clearly in Fig. 3, whichshows some of the blades of Fig. l enlarged. The rings 0 and o aredimensioned in such a way that their surface is very large in proportionto the sharp edges, so that in case of contact only the sharp edges comein contact and on account of very small surfaces being in contact, arelatively small amount of heat is generated; the small amount of heatis dissipated by the relatively large surfaces of the rings. In thistype of gland it is impossible for contact to take place on largesurfaces and therefore it is impossible for a large amount of heat to begenerated through friction.

The sleeve 0 is attached flexibly to the shaft; at one end a nut (Z isscrewed on the shaft, this nut being provided with a thin ring a. Thisthin ring surrounds at its free end the end of the sleeve. At the otherend the sleeve is attached to the shaft by means of four keys 7 shownalso in Figure 2. These keys prevent the rotation of the sleeve on theshaft; further, the keys f are arranged crosswise so that the sleeve (6can expand radially with complete freedom while its centre linecoincides all the time with the centre line of the shaft. The sleeve ais further fixed at one end longitudinally to the shaft by means of anut g screwed on the shaft and provided with a small retaining ring hresting against a similar retaining ring 2' on the sleeve a.

Clearances are provided between the nut (Z with its ring 6 and thesleeve so that the sleeve a can expand longitudinally with completefreedom from the ring ft in accordance with the relative temperatures ofthe sleeve and the shaft itself. This construction allows free expansionof the sleeve (in in a longitudinal direction irrespective of thetemperature of the shaft, since the sleeve is retained at one end onlyby the flange 71, which prevents the sleeve from being capable of bodilymovement in an axial direction along the shaft. The construction alsoallows substantial; freedom of expansion of the sleeve radially, sincebetween the sleeve a and the radially inner face of the flange 71, andbetween the-radially outer face of the flange 2' and the radially innerface ofthe nut g are annular spaces allowing of radial ex pansion; sincethe keysf allow the sleeve freedom of=movement in a radial direction;

andsince a deep annular recess is out in the.

nut 01, the ring 6, the thickness of which is small compared with thethickness of the body of the nut, may follow the movements of the endportion of the sleeve a as it eX- pands or contracts radially.

The stationary part b of the gland is also connected by flexible meansto the casing. It has flanges is, each flange being provided with ringsZ. These rings surround'similar rings on on the casing. This arrangementmakes the stationary part of the gland con centric with the casing andalso with the shaft and naturally with the gland sleeve a. In suitablerecesses in the casing are lodged flexible rings a which press againstthe stationary part Z) concentrically. These rings are prevented fromfalling out by shields or some other means. Usually the stationary partZ) has a higher temperature than the casing 79. It will thereforeexpand. more than the casing. In expanding radially the rings 71 wouldbe compressed but as these rings are uniform all round the stationarypart i) would remain concentric while expanding freely in the radialdirection. longitudinal direction the stationary part Z) is fixed bymeans of rings 1' in the casing. The expansion in longitudinal directiontakes place in both directions away from these rings. The gland issealed by steam from inside the casing, or should the pressure be lowerthan the pressure outside the casing, steam is admitted to the space afrom which it reaches through openings the space i in the labyrinths andseals the gland. In the space the steam pressure is maintained slightlyabove the pressure outside. of the casing, the steam will therefore leakalso through a number of labyrinths to the space "Lb from where it maybe taken out through the channel 11 outside of the casing, or any othersuitable space.

Figure 3 shows in' greater detail the labyrinth of the gland. It will beseen that the small clearances are formed. by sharp edges of rings, onebeing provided on the stationary part, the other on the rotating part ofthe gland. fraction of the Surface of the rings 0 and 0.

Figure 4 represents an alternative construction in which the rings conthe sleeve are alternately of larger and smaller diameter, correspondingto ring 0 on the stationary part of alternately smaller and largerdiameter. The steam leaking for instance through the clearance of thefirst ring does not only fill thespace as in which the kinetic energy ofthe steam is destroyed but in addition the next clearanceisona differentdiameter, so that the flow of leaking steam is bafi'led.

Figure 5 represents anotheralternative construction of our invention.The longitudinal spacing o-f'the rings c-on the sleeveis different fromthe spacing. ofrings- 0' on The edge represents a small the stationaryportion 6. It may be that there is a relative movement in thelongitudinal direction between the sleeve a and stationary portion 6. Ifsuch movement takes place the rings 0 and c are not exactly opposite; infact in certain conditions vthe rings 0 may be just midway between therings 0 and the-leakage would obviouslybe increased owing to theincreased clearances. In this alternative construction this cannot takeplace. Some of the rings will be Opposite, some will have only smallclearances and only a comparatively small proportion will have aclearance equal to half the pitch.

In Figure 6 another alternative construction is shown. The rings 0. andc are not made'out of one piece with the sleeve 01' the body of thestationary part, but they are formed of thin rings with distance pieces9 and 2 between them. In this {manner the same object is'achieved aswith the construction shown in Figure 8.

In Figure 7 the rings 0 and 0 are made separately and held in onecertain position by distance rings.

In order to prevent any steam flow to reach from one clearance to thenext clearance directly, baffle plates 5 are fixed so that the leakingsteammust change its direction of flow before it passes fromoneclearance to the next clearance.

It should be understood that in principle the constructions describedare applicable, not only for packings between the shaft and the casing,but between, for instance, diaphragms and the rotor, or generallybetween the rotor and stator.

In cases where the pressure on the one side of the packing gland isalways higher than the pressure on the other side, such as is the casewith diaphragms there is no need to arrange for additional sealing ofthe glands by means of steam being admitted to intermediate spaces inthe gland.

The gland illustrated by way of example in the drawings is suitable foruse in cases wherein, owing to substantial changes of temperatureoccurring at the gland from time totime, the operation of the gland, if

mounted directly on the machine parts between which relative motionoccurs, would be affected adversely. It is clear that in large glands itis desirable to allow for appreciable axial movement in the case ofcylindrical glands, and. appreciable radial movement in the case ofradial glands, if they are liable to be subjected to considerablechanges in temperature.

According to the present invention, the stationary and rotating part ofthe gland are made ofmaterials having substantially the same temperatureexpansion; as the temperature over the gland is practically uniform andas the temperature expansion of the metals is substantially the same,the

clearances will remain the sameindependently of: the practically uniformtemperature prevailing in the gland at any one time. I

It should be understood that'the present invention is applicable, notonly to steam turbines, but generally to elastic fluid turbines, rotaryair and gas compressors, ro-

tary pumps and generally to all such rotary machinery where leakages areto be kept within small limits between spaces of higher and lowerpressures.

I claim 1. A labyrinth packing gland, comprising a rotary member,annular sharp-edged proximity to the sharp edges on the other memberthan to any other part of the said other member.

2. A labyrinth packing gland, comprising a rotary member, annularsharp-edged blades projecting from the rotary member, astationarymember, annular sharp-edged blades which project from thestationary member in a direction substantially parallel to that of theblades projecting from the rotary member, and which are arranged sothat,'for each member, the sharp edges on that member are situated incloser proximity to the sharp edges on the other member than to anyother part of the said other member, means which hold the rotary memberin position but allow radial expansion thereof, and means which hold thestationary member in position but allow radial expansion thereof.

3. A labyrinth packing gland, comprising a rotary sleeve associated withY a shaft, annular sharp-edged blades projecting from the rotary sleeve,a stationary sleeve associated with a stationary support, annularsharp-edged blades which project from the stationary sleeve in adirection substantially parallel to that of the blades projectingfrointhe rotary sleeve, and which are arranged so that their sharp edges aresituated in close proximity to the sharp edges of the blades on therotary sleeve, means for holding the rotary sleeve in position andallowing radial and axial expansion thereof, and means for holding thestationary sleeve in a position concentric with the rotary sleeve, andallowing radial and axial expansion of the said stationary sleeve.

4. A labyrinth packing gland, comprising a rotary sleeve surrounding ashaft, means for holding the sleeve in position and allowing radial andaxial expansion thereof, 0on1- prising means for drawing the end of thesleeve against a shoulder on the shaft, and at 'least two keys engagingkey ways in the sleeve and shaft and arranged on dilferent diameters ofthe shaft, annular sharp-edged blades projecting from the rotary sleeve,a

'tion substantially parallel to that of the blades on the rotary sleeve,and which are arranged so that their sharp edges are situated in closeproximity to the sharp edges of the latter blades, and means for holdingthe stationary sleeve in a position concentric with the rotary sleeveand allowing radial and axial expansion of the said stationary sleeve.

5. A labyrinth packing gland, comprising a rotary member, annularsharp-edged blades projecting therefrom, a stationary member, a supportfor the stationary member, annular sharp-edged blades which project fromthe stationary member in a direction substantially parallel to that ofthe blades on the rotary member, and which are arranged neaaoss 'rectlypositioned relative to the rotary mem- "ber.

6. A labyrinth packing gland, comprising a rotary member, annularsharp-edged blades projecting from the rotary member, a stationarymember of material of substantially the same temperature expansion asthat of the rotary member, and annular sharp-edged blades whichprojectfrom the stationary member in a direction substantially parallel to thatof the blades on the rotary member and which are arranged so that, foreach member, the sharp edges on that member are situated in closerproximity to the sharp edges on the other member than to any other partof the said other member.

7. A labyrinth packing gland, comprising a rotary member, annularsharp-edged blades, projecting therefrom, a stationary member, andannular sharp-edged blades projecting therefrom in a directionsubstantially paralel to that of the blades on, the rotary member, andwhich are arranged so that, for each member the sharp edges on thatmember are situated in closer proximity to the sharp edges-on the othermember than to any other part of the said other member, and wherein thespacingof the blades on the one member is different from the spacing ofthe blades on the other member.

BLEDRIGH POCHOBRADSKY.

